Electrolysis device

Abstract

An electrolysis device 10 comprises: a plurality of electrolytic cells 11; a plurality of rectifiers 12; a control unit 16; a storage unit 17; a plurality of temperature sensors 15; and a plurality of voltage sensors 14. The control unit 16: acquires a power command; reads, from the storage unit 17, current-voltage characteristics corresponding to respective temperatures of the plurality of electrolytic cells 11 detected by the plurality of temperature sensors 15; controls, in response to the power command, current distribution amounts on the basis of the current-voltage characteristics of the plurality of electrolytic cells 11 read from the storage unit 17 so that a sum of amounts of gas generated by the plurality of electrolytic cells 11 is maximized; and updates the current-voltage characteristics stored in the storage unit 17 at a predetermined time interval on the basis of a difference between the voltages detected by the voltage sensors 14 and estimated values of the voltages of the electrolytic cells 11 corresponding to the current distribution amount, the estimated values being calculated from the current-voltage characteristics read from the storage unit 17.

Description

electrolyzer

[0001] This disclosure relates to an electrolytic device.

[0002] Conventionally, electrolytic devices that generate hydrogen and oxygen by electrolyzing water are known. Typically, an electrolytic device is equipped with an electrolytic cell, in which water is electrolyzed. In large-scale electrolytic devices, multiple electrolytic cells are often operated simultaneously to generate large quantities of hydrogen.

[0003] For example, Patent Document 1 discloses a hydrogen production facility that includes multiple cell stacks (electrolytic cells) and selects the number of cell stacks to be used so that the voltage and current acting on each cell stack are within a predetermined range.

[0004] Japanese Patent Publication No. 2005-126792

[0005] By using electricity generated from renewable energy sources such as solar and wind power to electrolyze water, it is possible to produce hydrogen while reducing carbon dioxide emissions.

[0006] Electricity generated from renewable energy sources is power that fluctuates over time. When using such fluctuating power to perform electrolysis and produce gases such as hydrogen, it is desirable to produce the gas efficiently.

[0007] In view of these circumstances, the purpose of this disclosure is to provide an electrolytic device that enables efficient gas generation when performing electrolysis using fluctuating power.

[0008] In other words, the present invention is as follows: [1] A plurality of electrolytic cells containing a liquid that is decomposed to generate gas when an electric current is supplied to it; a plurality of rectifiers installed in each of the plurality of electrolytic cells and supplying an electric current to each of the plurality of electrolytic cells; a control unit that controls the amount of current supplied by the plurality of rectifiers to the plurality of electrolytic cells; a storage unit that stores the current-voltage characteristics for each of the plurality of electrolytic cells for each temperature; a plurality of temperature sensors installed in each of the plurality of electrolytic cells and detecting the temperature of each of the plurality of electrolytic cells; a plurality of voltage sensors installed in each of the plurality of electrolytic cells and detecting the voltage of each of the plurality of electrolytic cells; the control unit acquires a power command that instructs the amount of power to be supplied to the plurality of electrolytic cells as a whole; reads out the current-voltage characteristics from the storage unit that correspond to the temperature of each of the plurality of electrolytic cells detected by the plurality of temperature sensors; and controls the amount of current supplied based on the current-voltage characteristics of the plurality of electrolytic cells read out from the storage unit so that the sum of the amount of gas generated by the plurality of electrolytic cells is maximized. Electrolytic apparatus that updates the current-voltage characteristics stored in the memory unit at predetermined intervals based on the difference between the voltage detected by the voltage sensor and the estimated voltage of the electrolytic cell according to the amount of current distribution, calculated from the current-voltage characteristics read from the memory unit. [2] Electrolytic apparatus according to [1], wherein the predetermined period is a time equal to or greater than the maximum transition time expressed by the following formula (1): Maximum transition time = (Upper limit of the allowable current value of the electrolytic cell - Lower limit of the allowable current value of the electrolytic cell) / Slope constraint (1) Here, the upper limit of the allowable current value of the electrolytic cell is the upper limit of the current that the electrolytic cell can supply, the lower limit of the allowable current value of the electrolytic cell is the lower limit of the current that the electrolytic cell can supply, and the slope constraint is the amount of current change that the current flowing through the electrolytic cell provided for film protection can change per unit time.[3] An electrolytic apparatus according to [1] or [2], wherein the control unit reads from the storage unit a predicted current-voltage characteristic corresponding to the temperature of the electrolytic cell, instead of reading from the storage unit a predicted current-voltage characteristic corresponding to the temperature of the electrolytic cell detected by the temperature sensor. [4] An electrolytic apparatus according to any one of [1] to [3], wherein the control unit predicts the temperature of the electrolytic cell based on a mass heat balance model. [5] An electrolytic apparatus according to any one of [1] to [4], wherein the control unit predicts the temperature of the electrolytic cell based on a model generated based on a relationship between the current flowing through the electrolytic cell and the temperature of the electrolytic cell, which has been measured in advance. [6] An electrolytic apparatus according to any one of [1] to [5], wherein the power instructed by the power command is power that fluctuates over time. [7] An electrolytic apparatus according to any one of [1] to [6], wherein the power instructed by the power command is power that fluctuates over time depending on the amount of electricity generated by renewable energy. [8] An electrolytic apparatus according to any one of [1] to [7], wherein the control unit controls the amount of current distribution by solving a nonlinear programming problem based on the power command and the current-voltage characteristics of the plurality of electrolytic cells so that the sum of the gas generation amounts is maximized. [9] An electrolytic apparatus according to any one of [1] to [8], wherein the control unit solves the nonlinear programming problem using any of successive quadratic programming, penalty function method, extended Lagrangian function method and interior point method.

[10] A plurality of electrolytic cells containing a liquid that is decomposed to generate gas when an electric current is supplied to it; a plurality of rectifiers installed in each of the plurality of electrolytic cells and supplying an electric current to each of the plurality of electrolytic cells; a control unit that controls the amount of current supplied by the plurality of rectifiers to the plurality of electrolytic cells; a storage unit that stores the current-voltage characteristics for each of the plurality of electrolytic cells for each temperature; a plurality of temperature sensors installed in each of the plurality of electrolytic cells and detecting the temperature of each of the plurality of electrolytic cells; a plurality of voltage sensors installed in each of the plurality of electrolytic cells and detecting the voltage of each of the plurality of electrolytic cells, wherein the control unit acquires a gas production amount command that indicates the amount of gas to be generated by the plurality of electrolytic cells in total; reads out the current-voltage characteristics corresponding to the temperature of each of the plurality of electrolytic cells detected by the plurality of temperature sensors from the storage unit; and controls the amount of current supplied based on the current-voltage characteristics of the plurality of electrolytic cells read out from the storage unit so that the sum of the power used by the plurality of electrolytic cells is minimized, based on the gas production amount command. An electrolytic device that updates the current-voltage characteristics stored in the memory unit at predetermined intervals based on the difference between the voltage detected by the voltage sensor and an estimated value of the voltage of the electrolytic cell corresponding to the amount of current distribution, calculated from the current-voltage characteristics read from the memory unit.

[0009] According to the electrolytic apparatus described herein, when generating gas by performing electrolysis using fluctuating power, gas can be generated efficiently.

[0010] This is a schematic diagram of an electrolytic device according to one embodiment. This is a diagram showing an example of the current-voltage characteristics of an electrolytic cell. This is a flowchart showing an example of the operation of an electrolytic device according to one embodiment. This is a diagram showing an example of the current-voltage characteristics when there are two electrolytic cells. This is a diagram showing an example of maximizing the amount of hydrogen produced when there are two electrolytic cells. This is a flowchart showing an example of the operation of selecting an electrolytic cell. This is a flowchart showing an example of the operation of updating the current-voltage characteristics of an electrolytic cell. This is a diagram schematically showing how the current-voltage characteristics of an electrolytic cell are updated. This is a conceptual diagram showing the operation of compensating for the difference between the power command and the actual value of power consumption. This is a schematic diagram of an electrolytic device according to a modified example. This is a flowchart showing an example of the operation of an electrolytic device according to a modified example. This is a diagram showing an example of the current-voltage characteristics when there are two electrolytic cells. This is a diagram showing an example of minimizing the amount of power consumed when there are two electrolytic cells. This is a conceptual diagram showing the operation of compensating for the difference between the gas production command and the actual value of gas production.

[0011] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0012] Figure 1 is a schematic diagram of an electrolytic apparatus 10 according to one embodiment. The configuration and function of the electrolytic apparatus 10 according to one embodiment will be described with reference to Figure 1.

[0013] The electrolytic device 10 is a device capable of electrolyzing a liquid. The liquid that the electrolytic device 10 electrolyzes is a liquid that is decomposed to generate gas when an electric current is supplied. The liquid may be, for example, water.

[0014] When the liquid is water, the electrolytic device 10 electrolyzes the water to generate hydrogen and oxygen as gases. The liquid that the electrolytic device 10 electrolyzes is not limited to water. The liquid may be, for example, saline solution. In the following description of embodiments, the case where the liquid is water will be used as an example.

[0015] The electrolytic device 10 comprises a plurality of electrolytic cells 11-1 to 11-n, a plurality of rectifiers 12-1 to 12-n, a plurality of current sensors 13-1 to 13-n, a plurality of voltage sensors 14-1 to 14-n, a plurality of temperature sensors 15-1 to 15-n, a control unit 16, and a storage unit 17.

[0016] In this embodiment, an example is shown in which the electrolytic apparatus 10 comprises n electrolytic cells 11-1 to 11-n, n rectifiers 12-1 to 12-n, n current sensors 13-1 to 13-n, n voltage sensors 14-1 to 14-n, and n temperature sensors 15-1 to 15-n. n may be any integer of 2 or more.

[0017] Electrolytic cells 11-1 to 11-n may be simply referred to as "electrolytic cell 11" when there is no need to distinguish between them. Rectifiers 12-1 to 12-n may be simply referred to as "rectifier 12" when there is no need to distinguish between them. Current sensors 13-1 to 13-n may be simply referred to as "current sensor 13" when there is no need to distinguish between them. Voltage sensors 14-1 to 14-n may be simply referred to as "voltage sensor 14" when there is no need to distinguish between them. Temperature sensors 15-1 to 15-n may be simply referred to as "temperature sensor 15" when there is no need to distinguish between them.

[0018] The electrolytic cell 11 contains the liquid to be electrolyzed. The liquid contained in the electrolytic cell 11 is a liquid that is decomposed to generate gas when an electric current is supplied. The electrolytic cell 11 may be any electrolytic cell capable of electrolyzing a liquid. The liquid may be supplied to the electrolytic cell 11 by a pump or the like. In this embodiment, the case where the liquid is water will be explained as an example.

[0019] The electrolytic cell 11 is equipped with an anode and a cathode as electrodes. When a voltage is applied between the anode and cathode of the electrolytic cell 11, and an electric current flows through the water contained in the electrolytic cell 11, the water is electrolyzed, and hydrogen and oxygen are produced.

[0020] In the electrolyzer 11, the generated hydrogen is sent to a hydrogen tank. The generated oxygen in the electrolyzer 11 is sent to an oxygen tank. In FIG. 1, the illustration of the hydrogen tank and the oxygen tank is omitted.

[0021] The rectifiers 12-1 to 12-n are respectively installed in the electrolyzers 11-1 to 11-n. The rectifiers 12-1 to 12-n can respectively supply current to the electrolyzers 11-1 to 11-n.

[0022] The rectifiers 12-1 to 12-n are supplied with power from the power generation device 1 outside the electrolysis device 10.

[0023] The power generation device 1 is a power generation device that generates electricity by renewable energy. The renewable energy may be, for example, sunlight, wind power, hydropower, and geothermal energy. Since the power generation device 1 generates electricity by renewable energy, the power supplied by the power generation device 1 to the rectifiers 12-1 to 12-n varies with time.

[0024] The rectifier 12 is electrically connected to the anode and cathode of the electrolyzer 11. The rectifier 12 converts the power supplied from the power generation device 1 into direct current and supplies a current between the anode and cathode of the electrolyzer 11. The current supplied by the rectifier 12 flows into the water contained in the electrolyzer 11.

[0025] The rectifier 12 can control the magnitude of the current supplied to the electrolyzer 11 according to a command from the control unit 16.

[0026] The rectifier 12 may be a rectifier of any configuration that can control the magnitude of the supplied current.

[0027] The current sensors 13-1 to 13-n are respectively installed in the electrolyzers 11-1 to 11-n. The current sensors 13-1 to 13-n can respectively detect the current of the electrolyzers 11-1 to 11-n.

[0028] Here, the current of the electrolyzer 11 means the current supplied by the rectifier 12 to the electrolyzer 11 and flowing between the anode and cathode of the electrolyzer 11.

[0029] The current sensor 13 may be a current sensor with any configuration.

[0030] The current sensor 13 outputs the detected current value to the control unit 16. Note that the connection between the current sensor 13 and the control unit 16 is not shown in Figure 1.

[0031] Voltage sensors 14-1 to 14-n are installed in electrolytic cells 11-1 to 11-n, respectively. Voltage sensors 14-1 to 14-n can detect the voltage of electrolytic cells 11-1 to 11-n, respectively.

[0032] Here, the voltage of the electrolytic cell 11 refers to the voltage between the anode and cathode of the electrolytic cell 11.

[0033] The voltage sensor 14 may be a voltage sensor with any configuration.

[0034] The voltage sensor 14 outputs the detected voltage value to the control unit 16. Note that the connection between the voltage sensor 14 and the control unit 16 is not shown in Figure 1.

[0035] Temperature sensors 15-1 to 15-n are installed in electrolytic cells 11-1 to 11-n, respectively. Each of the temperature sensors 15-1 to 15-n can detect the temperature of the electrolytic cells 11-1 to 11-n.

[0036] The temperature sensor 15 may be any temperature sensor with any configuration.

[0037] The temperature sensor 15 outputs the detected temperature value to the control unit 16. Note that the connection between the temperature sensor 15 and the control unit 16 is not shown in Figure 1.

[0038] The control unit 16 controls the entire electrolytic device 10 and each block of the electrolytic device 10. The control unit 16 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0039] The control unit 16 obtains a power command from outside the electrolytic device 10. The power command is a command that instructs the power to be supplied to the entire group of electrolytic cells 11-1 to 11-n.

[0040] The power command may be, for example, a command sent by a server of the organization managing the power generator 1. The power command may be a command that fluctuates based on the amount of power generated by the power generator 1. That is, when the amount of power generated by the power generator 1 is large, the power indicated by the power command is large, and when the amount of power generated by the power generator 1 is small, the power indicated by the power command is small.

[0041] The amount of power generated by power generator 1 fluctuates over time. Therefore, the power command instructed by the power control unit fluctuates over time. Furthermore, since power generator 1 generates electricity using renewable energy, the power command instructed by the power control unit fluctuates over time depending on the amount of electricity generated from renewable energy.

[0042] Based on the acquired power command, the control unit 16 controls the distribution amount of current supplied by the multiple rectifiers 12-1 to 12-n to the multiple electrolytic cells 11-1 to 11-n so that the total amount of hydrogen generated (amount of gas generated) by the multiple electrolytic cells 11-1 to 11-n is maximized.

[0043] Details of the operation of the control unit 16 will be described later.

[0044] The storage unit 17 may be, for example, a semiconductor memory, magnetic memory, or optical memory. The storage unit 17 may function as, for example, a main memory, an auxiliary memory, or a cache memory. The storage unit 17 stores any information used in the operation of the electrolytic device 10. For example, the storage unit 17 may store a system program, an application program, and various other information.

[0045] The memory unit 17 stores the current-voltage characteristics for each of the multiple electrolytic cells 11-1 to 11-n at different temperatures. The current-voltage characteristics of the electrolytic cell 11 refer to the relationship between current and voltage when the rectifier 12 supplies current to the electrolytic cell 11 and current flows through the water contained in the electrolytic cell 11. The voltage at this time is the voltage between the anode and cathode of the electrolytic cell 11.

[0046] The current-voltage characteristics of each electrolytic cell 11 differ from one electrolytic cell 11 to another. Therefore, the memory unit 17 stores the current-voltage characteristics for each electrolytic cell 11. Furthermore, the current-voltage characteristics of each electrolytic cell 11 depend on the temperature of the electrolytic cell 11. Therefore, the memory unit 17 stores the current-voltage characteristics for each electrolytic cell 11 for each temperature.

[0047] The current-voltage characteristics of the electrolytic cell 11 stored in the memory unit 17 were created based on current and voltage measurements taken in advance.

[0048] Figure 2 shows an example of the current-voltage characteristics of a certain electrolytic cell 11 stored in the memory unit 17. In the example shown in Figure 2, the memory unit 17 stores the current-voltage characteristics of the electrolytic cell 11 when the temperature is 30°C, 50°C, 60°C, 70°C, 80°C, and 90°C. Note that the current-voltage characteristics shown in Figure 2 are just an example, and the memory unit 17 may store current-voltage characteristics at finer temperature intervals or at coarser temperature intervals.

[0049] The amount of hydrogen generated by the electrolytic cell 11 is proportional to the current in the electrolytic cell 11. The power consumption of the electrolytic cell 11 is the product of the current in the electrolytic cell 11 and the voltage in the electrolytic cell 11. Therefore, an electrolytic cell 11 with a lower voltage at the same current is considered a higher-performing electrolytic cell 11. This is because a lower voltage at the same current means that less power is consumed when generating the same amount of hydrogen.

[0050] The operation of the electrolytic device 10 will be explained with reference to the flowchart shown in Figure 3.

[0051] Step S101: The control unit 16 obtains a power command from outside the electrolytic device 10. The power command is a command that instructs the power to be supplied to the entire group of electrolytic cells 11-1 to 11-n. The power instructed by the power command fluctuates over time.

[0052] Step S102: The control unit 16 reads the upper and lower limits of the allowable current value of the electrolytic cell 11 from the storage unit 17.

[0053] The upper limit of the allowable current value for the electrolytic cell 11 is the upper limit of the current that the electrolytic cell 11 can supply. The lower limit of the allowable current value for the electrolytic cell 11 is the lower limit of the current that the electrolytic cell 11 can supply. The upper and lower limits of the allowable current value for the electrolytic cell 11 are stored in the memory unit 17.

[0054] Step S103: The control unit 16 obtains the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n from the temperature sensors 15-1 to 15-n.

[0055] Step S104: The control unit 16 reads from the storage unit 17 the current-voltage characteristics of the electrolytic cells 11-1 to 11-n that correspond to the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n.

[0056] For example, if the temperature of the electrolytic cell 11-1 detected by the temperature sensor 15-1 is 60°C, the control unit 16 reads the current-voltage characteristics of the electrolytic cell 11-1 stored in the memory unit 17 for when the temperature is 60°C. The control unit 16 reads the current-voltage characteristics of the other electrolytic cells 11-2 to 11-n in the same manner.

[0057] Step S105: Based on the power command acquired in step S101 and the current-voltage characteristics of the plurality of electrolytic cells 11-1 to 11-n read from the storage unit 17 in step S104, the control unit 16 calculates the current distribution amount at which the total amount of hydrogen generation becomes maximum.

[0058] A method by which the control unit 16 calculates the current distribution amount at which the total amount of hydrogen generation becomes maximum will be described in more detail.

[0059] The power P of the electrolytic cell 11-i ｉ is expressed as in the following formula (1). Here, the electrolytic cell 11-i means the i-th electrolytic cell 11 among the electrolytic cells 11-1 to 11-n. P ｉ = E ｃｉ (I ｉ , T ｉ ) I ｉ (1) Here, I ｉ is the current of the electrolytic cell 11-i. T ｉ is the temperature of the electrolytic cell 11-i. E ｃｉ (I ｉ , T ｉ ) is the voltage of the electrolytic cell 11-i.

[0060] The voltage E ｃｉ (I ｉ , T ｉ ) shows the current I ｉ and the temperature T ｉ in the parentheses, which means that the voltage E ｃｉ is a function of the current I ｉ and the temperature T ｉ . Specifically, the control unit 16 reads the current-voltage characteristics with respect to the temperature T ｉ of the electrolytic cell 11-i from the storage unit 17, and reads the voltage corresponding to the current I ｉ in the read current-voltage characteristics, thereby reading the voltage E ｃｉ .

[0061] The hydrogen generation amount F ｉ generated by the electrolytic cell 11-i is expressed as in the following formula (2). F ｉ = I ｉα (2) Here, α is a coefficient.

[0062] The control unit 16 solves a nonlinear programming problem so as to maximize the total amount of hydrogen generated by the electrolytic cells 11-1 to 11-n, and calculates the distribution amount of current supplied to the electrolytic cells 11-1 to 11-n.

[0063] The objective function used by the control unit 16 to solve the nonlinear programming problem is expressed as shown in equation (3) below.

[0064] The constraints on the control unit 16 when solving the nonlinear programming problem are expressed as shown in equations (4) and (5) below. Here, P ｒｅｑ This is the power directed by the power command. Here, l ｂ This is the lower limit of the allowable current value. ｂ This is the upper limit of the allowable current value.

[0065] As described above, the control unit 16 solves a nonlinear programming problem using equation (3) as the objective function and equations (4) and (5) as constraints, so as to maximize the total amount of hydrogen generated by electrolytic cells 11-1 to 11-n, and calculates the distribution amount of current supplied to electrolytic cells 11-1 to 11-n.

[0066] The control unit 16 may solve the nonlinear programming problem using, for example, successive quadratic programming, penalty function method, extended Lagrangian function method, or interior point method.

[0067] Step S106: The control unit 16 calculates the amount of current to be distributed to the electrolytic cells 11-1 to 11-n, and then controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n according to the calculated amount of current to be distributed.

[0068] <Specific Example> Referring to Figures 4 and 5, an example of a specific case in which the control unit 16 solves a nonlinear programming problem is shown.

[0069] As a concrete example, we will explain the case where there are two electrolytic cells 11, i.e., n = 2. Furthermore, the values ​​of the various parameters are assumed to be as follows: α = 1 P ｒｅｑ = 50 [kW] u ｂ= 10 [kA] l ｂ = 1 [kA] T １ = 30 [℃] T ２ = 40 [℃]

[0070] Figure 4 is a graph showing the current-voltage characteristics of electrolytic cell 11-1 and electrolytic cell 11-2 when the various parameters are set to the values ​​described above.

[0071] The graph on the left of Figure 4 shows the current-voltage characteristics of electrolytic cell 11-1 at 30°C. The graph on the right of Figure 4 shows the current-voltage characteristics of electrolytic cell 11-2 at 40°C.

[0072] The control unit 16 reads the two current-voltage characteristics shown in Figure 4 from the storage unit 17.

[0073] Figure 5 is a table showing how the control unit 16 solves a nonlinear programming problem using sequential quadratic programming.

[0074] In Figure 5, I1 and E1 represent the current and voltage of electrolytic cell 11-1, respectively. I2 and E2 represent the current and voltage of electrolytic cell 11-2, respectively. P1 and P2 represent the power of electrolytic cell 11-1 and the power of electrolytic cell 11-2, respectively. I1 + I2 represents the sum of the current I1 of electrolytic cell 11-1 and the current I2 of electrolytic cell 11-2. P represents the sum of the power P1 of electrolytic cell 11-1 and the power P2 of electrolytic cell 11-2.

[0075] When the control unit 16 solves the nonlinear programming problem, it sets the following constraints: P = 50 [kW], 1 [kA] ≤ I1 ≤ 10 [kA], and 1 [kA] ≤ I2 ≤ 10 [kA].

[0076] When solving the nonlinear programming problem, the control unit 16 sets the objective function to maximize I1 + I2.

[0077] Referring to Figure 5, when I1 = 7 [kA] and I2 = 7.4 [kA], I1 + I2 is maximized. Therefore, the control unit 16 controls rectifiers 12-1 and 12-2 so that I1 = 7 [kA] and I2 = 7.4 [kA].

[0078] <Selection of Electrolytic Cells> The electrolytic device 10 does not have to supply current to all of the electrolytic cells 11-1 to 11-n to perform electrolysis, but may supply current to only a select few electrolytic cells 11 to perform electrolysis. For example, if there are four electrolytic cells 11, i.e., n=4, the electrolytic device 10 may supply current to only three of those electrolytic cells 11 to perform electrolysis.

[0079] Referring to the flowchart shown in Figure 6, the process of selecting the electrolytic cell 11 to supply current will be explained.

[0080] Step S201: The control unit 16 obtains a power command from outside the electrolytic device 10.

[0081] Step S202: The control unit 16 obtains the voltages of the electrolytic cells 11-1 to 11-n detected by the voltage sensors 14-1 to 14-n from the voltage sensors 14-1 to 14-n.

[0082] Step S203: The control unit 16 determines the number of operating electrolytic cells 11. The control unit 16 always stores the number of operating electrolytic cells 11 in the storage unit 17. The control unit 16 determines the number of operating electrolytic cells 11 by reading the number of operating electrolytic cells 11 from the storage unit 17. For example, if the number of operating electrolytic cells 11 stored in the storage unit 17 is 3, the control unit 16 determines that there are 3 operating electrolytic cells 11.

[0083] Step S204: The control unit 16 calculates the filter value of the voltage of the electrolytic cell 11 obtained from the voltage sensor 14. Here, the filter value means the value obtained by passing the voltage of the electrolytic cell 11 through a low-pass filter. The control unit 16 may, for example, calculate the filter value by passing the voltage of the electrolytic cell 11 obtained from the voltage sensor 14 through a digital filter. Alternatively, for example, the control unit 16 may obtain the filter value by passing the voltage of the electrolytic cell 11 obtained from the voltage sensor 14 through an analog filter.

[0084] Step S205: The control unit 16 calculates the average value of the voltage of the electrolytic cell 11 based on the filter value of the voltage of the electrolytic cell 11. For example, the control unit 16 may calculate the average value of the voltage of the electrolytic cell 11 based on the following formula (6). Here, m is the number of operating electrolytic cells 11. ｆ，ｉ (t) is the filter value of the voltage of the electrolytic cell 11.

[0085] Step S206: The control unit 16 calculates the total current supplied to the multiple operating electrolytic cells 11 based on the average value of the voltages of the electrolytic cells 11 calculated by equation (6) above and the power command. For example, the control unit 16 calculates the total current supplied to the multiple operating electrolytic cells 11 based on the following equation (7): ａｌｌ You may calculate (t).

[0086] Step S207: The control unit 16 reads the lower limit of the allowable current value of the electrolytic cell 11 from the storage unit 17.

[0087] Step S208: The control unit 16 calculates the number of electrolytic cells 11 to supply current based on the total current calculated by equation (7) above and the lower limit of the allowable current value of the electrolytic cell 11. For example, if the total current is 1.25 [kA] and the lower limit of the allowable current value of the electrolytic cell 11 is 1 [kA], the control unit 16 calculates that the number of electrolytic cells 11 to supply current is 1.

[0088] Step S209: The control unit 16 obtains the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n from the temperature sensors 15-1 to 15-n.

[0089] Step S210: The control unit 16 reads from the storage unit 17 the current-voltage characteristics of the electrolytic cells 11-1 to 11-n that correspond to the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n.

[0090] Step S211: The control unit 16 selects which of the electrolytic cells 11-1 to 11-n to supply current to, based on the current-voltage characteristics of the electrolytic cells 11-1 to 11-n read from the storage unit 17 in step S210 and the number of electrolytic cells 11 to supply current calculated in step S208. The control unit 16 selects the number of electrolytic cells 11 to supply current calculated in step S208 that have a smaller voltage when compared with the same current.

[0091] When the control unit 16 selects an electrolytic cell 11, it may execute the flowchart shown in Figure 3 for the selected electrolytic cell 11.

[0092] <Updating Current-Voltage Characteristics> The electrolytic device 10 executes the process shown in the flowchart of Figure 3 and controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n with the calculated current distribution amount. After that, based on the voltage detected by the voltage sensor 14, the current-voltage characteristics stored in the memory unit 17 may be updated at predetermined intervals. The current-voltage characteristics of the electrolytic cell 11 change as the electrolytic cell 11 deteriorates, but by updating the current-voltage characteristics stored in the memory unit 17 at predetermined intervals, changes in the current-voltage characteristics due to the deterioration of the electrolytic cell 11 can be appropriately corrected.

[0093] Referring to the flowchart shown in Figure 7, the process by which the electrolytic device 10 updates its current-voltage characteristics will be explained.

[0094] Step S301: When the control unit 16 controls the rectifiers 12-1 to 12-n, it obtains the voltages of the electrolytic cells 11-1 to 11-n detected by the voltage sensors 14-1 to 14-n from the voltage sensors 14-1 to 14-n.

[0095] Step S302: The control unit 16 calculates an estimated value of the voltage of the electrolytic cell 11 from the current-voltage characteristics read from the storage unit 17. At this time, the control unit 16 calculates an estimated value of the voltage of the electrolytic cell 11 based on the distribution amount of current supplied to the electrolytic cell 11 and the current-voltage characteristics.

[0096] Step S303: The control unit 16 calculates the difference between the measured voltage detected by the voltage sensor 14 and the calculated estimated voltage for each electrolytic cell 11.

[0097] Step S304: The control unit 16 updates the current-voltage characteristics stored in the memory unit 17 based on the calculated difference.

[0098] Figure 8 shows an example of how the current-voltage characteristics are updated.

[0099] The left-hand diagram in Figure 8 shows an example of the current-voltage characteristics before the update. Graph 101 shows the current-voltage characteristics before the update. Reference numeral 102 indicates the estimated voltage. Reference numeral 103 indicates the measured voltage. Reference numeral 104 indicates the difference between the measured voltage and the estimated voltage.

[0100] The right-hand figure in Figure 8 shows an example of the current-voltage characteristics after the update. Graph 101 shows the current-voltage characteristics before the update. Reference numeral 103 indicates the measured voltage value. Reference numeral 104 indicates the difference between the measured voltage value and the estimated voltage value. Graph 105 shows the current-voltage characteristics after the update.

[0101] As shown in the right-hand diagram of Figure 8, the control unit 16 may add the difference between the measured voltage detected by the voltage sensor 14 and the calculated estimated voltage to the current-voltage characteristics before the update to obtain the updated current-voltage characteristics.

[0102] <Period for updating current-voltage characteristics> As described above, the control unit 16 may update the current-voltage characteristics stored in the memory unit 17 at predetermined intervals, but the predetermined period may be, for example, a time equal to or greater than the maximum transition time expressed by the following equation (8). Maximum transition time = (Upper limit of allowable current value of electrolytic cell - Lower limit of allowable current value of electrolytic cell) / Slope constraint (8) Here, the upper limit of the allowable current value of the electrolytic cell 11 is the upper limit of the current that the electrolytic cell 11 can supply. The lower limit of the allowable current value of the electrolytic cell 11 is the lower limit of the current that the electrolytic cell 11 can supply. The slope constraint is the amount of current change that the current flowing through the electrolytic cell 11 can change per unit time.

[0103] The slope constraint will be explained in detail. The electrolytic cell 11 usually has an electrolyte membrane. If the current flowing through the electrolytic cell 11 changes abruptly, the electrolyte membrane may deteriorate. Therefore, it is desirable to protect the electrolyte membrane by restricting the amount of current change that can be applied to the electrolytic cell 11 per unit time, so that the current flowing through the electrolytic cell 11 does not change abruptly. The slope constraint is intended to protect the electrolyte membrane by defining the amount of current change that can be applied to the electrolytic cell 11 per unit time.

[0104] The current in the electrolytic cell 11 changes to its maximum extent when it changes from the upper limit of the allowable current value of the electrolytic cell 11 to the lower limit of the allowable current value of the electrolytic cell 11, or when it changes from the lower limit of the allowable current value of the electrolytic cell 11 to the upper limit of the allowable current value of the electrolytic cell 11. In this case, the time it takes for the current flowing through the electrolytic cell 11 to change from the upper limit of the allowable current value to the lower limit, or the time it takes for the current flowing through the electrolytic cell 11 to change from the lower limit of the allowable current value to the upper limit, is the maximum transition time shown in equation (8) above.

[0105] In other words, when the control unit 16 controls the rectifier 12 to change the current flowing through the electrolytic cell 11, the current flowing through the electrolytic cell 11 will transition to the desired current after a time equal to or greater than the maximum transition time has elapsed. Therefore, when the control unit 16 updates the current-voltage characteristics stored in the memory unit 17 at predetermined intervals, if the predetermined interval is set to be longer than or equal to the maximum transition time represented by equation (8), the current-voltage characteristics can be updated without updating them while the current flowing through the electrolytic cell 11 is transitioning, and only after the current flowing through the electrolytic cell 11 has transitioned to the desired current.

[0106] <Utilization of Predicted Temperature> In the explanation of step S103 in the flowchart of Figure 3 described above, the control unit 16 obtained the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n from the temperature sensors 15-1 to 15-n. Also, in the explanation of step S104, the control unit 16 read out the current-voltage characteristics of the electrolytic cells 11-1 to 11-n corresponding to the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n from the storage unit 17.

[0107] Instead of performing steps S103 and S104, the control unit 16 may, instead of acquiring the temperature of the electrolytic cell 11 detected by the temperature sensor 15 and reading the current-voltage characteristics corresponding to the acquired temperature from the storage unit 17, predict the temperature of the electrolytic cell 11 after the maximum transition time and read the current-voltage characteristics corresponding to the predicted temperature of the electrolytic cell 11 from the storage unit 17.

[0108] When the current flowing through the electrolytic cell 11 is changed, the temperature of the electrolytic cell 11 rises or falls. The control unit 16 may predict such temperature changes in the electrolytic cell 11 and read out the current-voltage characteristics corresponding to the predicted temperature of the electrolytic cell 11 from the storage unit 17.

[0109] The control unit 16 may predict the temperature of the electrolytic cell 11 based, for example, on a mass heat balance model.

[0110] Alternatively, the control unit 16 may predict the temperature of the electrolytic cell 11 based on a model generated based on the relationship between the current flowing through the electrolytic cell 11 and the temperature of the electrolytic cell 11, which has been measured in advance. In this case, the current flowing through the electrolytic cell 11 may be changed and the temperature of the electrolytic cell 11 at that time may be measured in advance, and the model generated based on the measurement results may be stored in the storage unit 17 beforehand.

[0111] <Compensation for the difference between the power command and the actual value> When the electrolytic device 10 executes the process shown in the flowchart of Figure 3, it controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n with the calculated current distribution amount. In this case, the power value instructed by the power command and the actual value of the sum of the power used by the multiple electrolytic cells 11-1 to 11-n should ideally be the same value, but there are cases where the power value instructed by the power command and the actual value of the sum of the power used do not match. In this case, the electrolytic device 10 may control the amount of current distributed to the electrolytic cells 11-1 to 11-n to compensate for the difference between the power value instructed by the power command and the actual value of the sum of the power used.

[0112] Figure 9 is a conceptual diagram illustrating the operation of compensating for the difference between the power value instructed by the power command and the actual power consumption.

[0113] When the control unit 16 controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n according to the calculated current distribution amount, the rectifiers 12-1 to 12-n consume power. In addition, power is consumed as disturbance by devices other than the rectifiers 12-1 to 12-n.

[0114] The actual power consumption of the electrolytic device 10 is the sum of the power consumed by the rectifiers 12-1 to 12-n and the power consumed as disturbances. The control unit 16 can calculate the power consumed by the rectifiers 12-1 to 12-n based on the current of each electrolytic cell 11 detected by the current sensor 13 and the voltage of each electrolytic cell 11 detected by the voltage sensor 14.

[0115] The control unit 16 may perform PID (Proportional-Integral-Differential) control on the difference between the actual power consumption and the power value instructed by the power command, and then perform a process to control the rectifiers 12-1 to 12-n using the sum of the power value instructed by the power command and the PID-controlled value as the power command in step S101 of Figure 3. In this way, the control unit 16 can compensate only for the difference between the actual power consumption and the power value instructed by the power command.

[0116] By performing this feedback process, the control unit 16 can compensate for the difference between the power value instructed by the power command and the actual value of the total power consumption.

[0117] As described above, the electrolytic apparatus 10 according to this embodiment includes a plurality of electrolytic cells 11-1 to 11-n that contain a liquid that is decomposed to generate gas when current is supplied, a plurality of rectifiers 12-1 to 12-n installed in each of the plurality of electrolytic cells 11-1 to 11-n and supplying current to each of the plurality of electrolytic cells 11-1 to 11-n, and a control unit 16 that controls the distribution amount of current supplied by the plurality of rectifiers 12-1 to 12-n to the plurality of electrolytic cells 11-1 to 11-n. The system includes a storage unit 17 that stores the current-voltage characteristics for each of the multiple electrolytic cells 11-1 to 11-n at different temperatures, multiple temperature sensors 15-1 to 15-n installed in each of the multiple electrolytic cells 11-1 to 11-n to detect the temperature of each of the multiple electrolytic cells 11-1 to 11-n, and multiple voltage sensors 14-1 to 14-n installed in each of the multiple electrolytic cells 11-1 to 11-n to detect the voltage of each of the multiple electrolytic cells 11-1 to 11-n. The control unit 16 then acquires a power command that instructs the total amount of power to be supplied to the multiple electrolytic cells 11-1 to 11-n, reads the current-voltage characteristics corresponding to the temperature of each of the multiple electrolytic cells 11-1 to 11-n detected by the multiple temperature sensors 15-1 to 15-n from the storage unit 17, and, based on the power command, controls the amount of current distribution based on the current-voltage characteristics of the multiple electrolytic cells 11-1 to 11-n read from the storage unit 17 so that the sum of the gas generation amounts generated by the multiple electrolytic cells 11-1 to 11-n is maximized, and updates the current-voltage characteristics stored in the storage unit 17 at predetermined intervals based on the difference between the voltage detected by the voltage sensor 14 and the estimated voltage of the electrolytic cell 11 according to the amount of current distribution, which is calculated from the current-voltage characteristics read from the storage unit 17. As a result, the electrolytic apparatus 10 according to this embodiment can control the distribution amount of current supplied by the multiple rectifiers 12-1 to 12-n to the multiple electrolytic cells 11-1 to 11-n so as to maximize the total amount of gas generated when it receives a power command that fluctuates over time. Therefore, the electrolytic apparatus 10 according to this embodiment can efficiently generate gas when performing electrolysis using fluctuating power to produce gas.Furthermore, the electrolytic device 10 according to this embodiment can efficiently generate gas by updating the current-voltage characteristics stored in the memory unit 17 at predetermined intervals. This allows for correction of changes in the current-voltage characteristics at predetermined intervals, even if differences in the performance of the electrolytic cell 11 arise due to differences in the original performance of the electrolytic cell 11 or deterioration of the electrolytic cell 11.

[0118] (Modified Version) Figure 10 is a schematic diagram of the electrolytic apparatus 10a according to the modified version. The electrolytic apparatus 10a according to the modified version will be described with reference to Figure 10.

[0119] The electrolytic device 10a comprises a plurality of electrolytic cells 11-1 to 11-n, a plurality of rectifiers 12-1 to 12-n, a plurality of current sensors 13-1 to 13-n, a plurality of voltage sensors 14-1 to 14-n, a plurality of temperature sensors 15-1 to 15-n, a control unit 16a, and a storage unit 17.

[0120] The modified electrolytic apparatus 10a differs from the electrolytic apparatus 10 shown in Figure 1 in that, instead of obtaining a power command, it obtains a gas production amount command from outside the electrolytic apparatus 10a. The gas production amount command is a command that indicates the total amount of gas to be generated by the multiple electrolytic cells 11-1 to 11-n. When the liquid electrolyzed by the modified electrolytic apparatus 10a is water, the amount of gas indicated by the gas production amount command is the amount of hydrogen.

[0121] Furthermore, the electrolytic apparatus 10a related to deformation differs from the electrolytic apparatus 10 shown in Figure 1 in that, when electrolyzing water based on the acquired gas production amount command, the multiple rectifiers 12-1 to 12-n control the distribution amount of current supplied to the multiple electrolytic cells 11-1 to 11-n so that the total amount of power used by the multiple electrolytic cells 11-1 to 11-n is minimized.

[0122] Regarding the modified electrolytic apparatus 10a, the differences from the electrolytic apparatus 10 shown in Figure 1 will be explained primarily, and explanations of points common to or similar with the electrolytic apparatus 10 shown in Figure 1 will be omitted as appropriate.

[0123] Referring to the flowchart shown in Figure 11, the operation of the modified electrolytic device 10a will be explained.

[0124] Step S401: The control unit 16a obtains a gas production amount command from outside the electrolytic device 10a. The gas production amount instructed by the gas production amount command fluctuates over time.

[0125] Step S402: The control unit 16a reads the upper and lower limits of the allowable current value of the electrolytic cell 11 from the storage unit 17.

[0126] Step S403: The control unit 16a obtains the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n from the temperature sensors 15-1 to 15-n.

[0127] Step S404: The control unit 16a reads from the storage unit 17 the current-voltage characteristics of the electrolytic cells 11-1 to 11-n that correspond to the temperatures of the electrolytic cells 11-1 to 11-n detected by the temperature sensors 15-1 to 15-n.

[0128] Step S405: The control unit 16a calculates the amount of current distribution that minimizes the total amount of power used, based on the gas production amount command acquired in step S401 and the current-voltage characteristics of the multiple electrolytic cells 11-1 to 11-n read from the storage unit 17 in step S404.

[0129] A more detailed explanation will be given regarding the method for calculating the current distribution amount that minimizes the total power used by the control unit 16a.

[0130] The control unit 16a solves a nonlinear programming problem so as to minimize the total power used by the electrolytic cells 11-1 to 11-n, and calculates the amount of current to be distributed to the electrolytic cells 11-1 to 11-n.

[0131] The objective function used by the control unit 16a to solve the nonlinear programming problem is expressed as shown in equation (9) below.

[0132] The constraints on the control unit 16a when solving the nonlinear programming problem are expressed as shown in equations (10) and (11) below. Here, F ｒｅｑ This is the amount of gas produced as instructed by the gas production directive. Here, l ｂ This is the lower limit of the allowable current value. ｂ This is the upper limit of the allowable current value.

[0133] As described above, the control unit 16a solves a nonlinear programming problem using equation (9) as the objective function and equations (10) and (11) as constraints, so as to minimize the total power used by the electrolytic cells 11-1 to 11-n, and calculates the distribution amount of current to supply to the electrolytic cells 11-1 to 11-n.

[0134] The control unit 16a may solve the nonlinear programming problem using, for example, successive quadratic programming, penalty function method, extended Lagrangian function method, or interior point method.

[0135] Step S406: The control unit 16a calculates the amount of current to be distributed to the electrolytic cells 11-1 to 11-n, and then controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n according to the calculated amount of current to be distributed.

[0136] In the modified electrolytic apparatus 10a, the rectifiers 12-1 to 12-n are controlled in such a way that the total power used by the electrolytic cells 11-1 to 11-n is minimized. As a result, the modified electrolytic apparatus 10a can efficiently produce hydrogen with low power consumption.

[0137] <Specific Examples of Modified Forms> Referring to Figures 12 and 13, an example of a specific case where the control unit 16a solves a nonlinear programming problem is shown.

[0138] As a concrete example, we will explain the case where there are two electrolytic cells 11, i.e., n = 2. Furthermore, the values ​​of the various parameters are assumed to be as follows: α = 1 F ｒｅｑ = 12[kA] u ｂ = 10 [kA] l ｂ = 1 [kA] T １ = 30 [℃] T ２ = 40 [℃]

[0139] Figure 12 is a graph showing the current-voltage characteristics of electrolytic cell 11-1 and electrolytic cell 11-2 when the various parameters are set to the values ​​described above.

[0140] The graph on the left in Figure 12 shows the current-voltage characteristics of electrolytic cell 11-1 at 30°C. The graph on the right in Figure 12 shows the current-voltage characteristics of electrolytic cell 11-2 at 40°C.

[0141] The control unit 16a reads the two current-voltage characteristics shown in Figure 12 from the storage unit 17.

[0142] Figure 13 is a table showing how the control unit 16a solves a nonlinear programming problem using successive quadratic programming.

[0143] In Figure 13, I1 and E1 represent the current and voltage of electrolytic cell 11-1, respectively. I2 and E2 represent the current and voltage of electrolytic cell 11-2, respectively. P1 and P2 represent the power of electrolytic cell 11-1 and the power of electrolytic cell 11-2, respectively. I1 + I2 represents the sum of the current I1 of electrolytic cell 11-1 and the current I2 of electrolytic cell 11-2. P represents the sum of the power P1 of electrolytic cell 11-1 and the power P2 of electrolytic cell 11-2.

[0144] When the control unit 16a solves the nonlinear programming problem, it imposes the following constraints: I1 + I2 = 12 [kA], 1 [kA] ≤ I1 ≤ 10 [kA], and 1 [kA] ≤ I2 ≤ 10 [kA].

[0145] The control unit 16a uses minimizing P as its objective function when solving a nonlinear programming problem.

[0146] Referring to Figure 13, P is minimized when I1 = 5 [kA] and I2 = 7 [kA]. Therefore, the control unit 16a controls rectifiers 12-1 and 12-2 so that I1 = 5 [kA] and I2 = 7 [kA].

[0147] <Compensation for the difference between the commanded gas production amount and the actual value in the modified example> When the electrolytic device 10a executes the process shown in the flowchart of Figure 11, it controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n with the calculated current distribution amount. In this case, the amount of gas produced instructed by the gas production amount command should ideally be the same as the actual amount of gas produced by the multiple electrolytic cells 11-1 to 11-n. However, there are cases where the amount of gas produced instructed by the gas production amount command and the actual amount of gas produced do not match. In this case, the electrolytic device 10a may control the distribution amount of current supplied to the electrolytic cells 11-1 to 11-n to compensate for the difference between the amount of gas produced instructed by the gas production amount command and the actual amount of gas produced.

[0148] Figure 14 is a conceptual diagram illustrating the operation that compensates for the difference between the gas production amount instructed by the gas production amount command and the actual gas production amount.

[0149] When the control unit 16a controls the rectifiers 12-1 to 12-n to supply current to the electrolytic cells 11-1 to 11-n according to the calculated current distribution amount, the rectifiers 12-1 to 12-n produce gas.

[0150] The control unit 16a can obtain the actual gas production amount produced by the rectifiers 12-1 to 12-n from a sensor capable of detecting the gas production amount.

[0151] The control unit 16a may perform PID control on the difference between the actual gas production amount and the gas production amount instructed by the gas production amount command, and then perform a process to control the rectifiers 12-1 to 12-n using the sum of the gas production amount instructed by the gas production amount command and the PID-controlled value as the gas production amount command in step S401 of Figure 11. In this way, the control unit 16a can compensate only for the difference between the actual gas production amount and the gas production amount instructed by the gas production amount command.

[0152] By performing this feedback process, the control unit 16a can compensate for the difference between the amount of gas produced instructed by the gas production command and the actual amount of gas produced.

[0153] Although the embodiments described above are representative examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of this disclosure. Therefore, the present invention should not be construed as being limited by the embodiments described above, and various modifications or changes are possible without departing from the claims.

[0154] For example, in the embodiment described above, the case in which the electrolytic device 10 is supplied with power from the power generation device 1 was used as an example, but the electrolytic device 10 may also be supplied with power from the commercial power grid.

[0155] For example, the details described for the electrolytic apparatus 10 in Figure 1, such as <selection of electrolytic cell>, <updating of current-voltage characteristics>, <period for updating current-voltage characteristics>, and <utilization of predicted temperature>, are also applicable to the modified electrolytic apparatus 10a shown in Figure 10.

[0156] 1. Power generation device 10, 10a. Electrolytic device 11. Electrolytic cell 12. Rectifier 13. Current sensor 14. Voltage sensor 15. Temperature sensor 16, 16a. Control unit 17. Memory unit

Claims

1. A plurality of electrolytic cells containing a liquid that is decomposed to generate gas when an electric current is supplied to it; a plurality of rectifiers installed in each of the plurality of electrolytic cells and supplying an electric current to each of the plurality of electrolytic cells; a control unit that controls the amount of current distributed by the plurality of rectifiers to the plurality of electrolytic cells; a storage unit that stores the current-voltage characteristics for each of the plurality of electrolytic cells at different temperatures; a plurality of temperature sensors installed in each of the plurality of electrolytic cells and detecting the temperature of each of the plurality of electrolytic cells; a plurality of voltage sensors installed in each of the plurality of electrolytic cells and detecting the voltage of each of the plurality of electrolytic cells; wherein the control unit acquires a power command that instructs the amount of power to be supplied to the plurality of electrolytic cells as a whole; reads out the current-voltage characteristics corresponding to the temperature of each of the plurality of electrolytic cells detected by the plurality of temperature sensors from the storage unit; and controls the amount of current distributed based on the current-voltage characteristics of the plurality of electrolytic cells read out from the storage unit so that the sum of the amount of gas generated by the plurality of electrolytic cells is maximized. An electrolytic device that updates the current-voltage characteristics stored in the memory unit at predetermined intervals based on the difference between the voltage detected by the voltage sensor and an estimated value of the voltage of the electrolytic cell corresponding to the amount of current distribution, calculated from the current-voltage characteristics read from the memory unit.

2. An electrolytic apparatus according to claim 1, wherein the predetermined period is a time equal to or greater than the maximum transition time expressed by the following formula (1): Maximum transition time = (Upper limit of the allowable current value of the electrolytic cell - Lower limit of the allowable current value of the electrolytic cell) / Slope constraint (1) Here, the upper limit of the allowable current value of the electrolytic cell is the upper limit of the current that the electrolytic cell can supply, the lower limit of the allowable current value of the electrolytic cell is the lower limit of the current that the electrolytic cell can supply, and the slope constraint is the amount of current change that the current flowing through the electrolytic cell can change per unit time.

3. An electrolytic apparatus according to claim 1, wherein the control unit reads from the storage unit a predicted current-voltage characteristic corresponding to the temperature of the electrolytic cell, instead of reading from the storage unit a current-voltage characteristic corresponding to the temperature of the electrolytic cell detected by the temperature sensor.

4. An electrolytic apparatus according to claim 3, wherein the control unit predicts the temperature of the electrolytic cell based on a mass heat balance model.

5. An electrolytic apparatus according to claim 3, wherein the control unit predicts the temperature of the electrolytic cell based on a model generated based on the relationship between the current flowing through the electrolytic cell and the temperature of the electrolytic cell, which has been measured in advance.

6. An electrolytic apparatus according to claim 1, wherein the power instructed by the power command is power that fluctuates with time.

7. An electrolytic apparatus according to claim 1, wherein the power instructed by the power command is power that fluctuates over time depending on the amount of electricity generated from renewable energy.

8. An electrolytic apparatus according to claim 1, wherein the control unit controls the amount of current distribution by solving a nonlinear programming problem based on the power command and the current-voltage characteristics of the plurality of electrolytic cells, such that the sum of the gas generation amounts is maximized.

9. An electrolytic apparatus according to claim 8, wherein the control unit solves the nonlinear programming problem using one of the following methods: successive quadratic programming, penalty function method, extended Lagrangian function method, and interior point method.

10. A plurality of electrolytic cells containing a liquid that is decomposed to generate gas when an electric current is supplied to it; a plurality of rectifiers installed in each of the plurality of electrolytic cells and supplying an electric current to each of the plurality of electrolytic cells; a control unit that controls the amount of current supplied by the plurality of rectifiers to the plurality of electrolytic cells; a storage unit that stores the current-voltage characteristics for each of the plurality of electrolytic cells at different temperatures; a plurality of temperature sensors installed in each of the plurality of electrolytic cells and detecting the temperature of each of the plurality of electrolytic cells; a plurality of voltage sensors installed in each of the plurality of electrolytic cells and detecting the voltage of each of the plurality of electrolytic cells, wherein the control unit acquires a gas production amount command that indicates the amount of gas to be generated by the plurality of electrolytic cells as a whole; reads out the current-voltage characteristics corresponding to the temperatures of each of the plurality of electrolytic cells detected by the plurality of temperature sensors from the storage unit; and controls the amount of current distribution based on the current-voltage characteristics of the plurality of electrolytic cells read out from the storage unit so as to minimize the total amount of power used by the plurality of electrolytic cells, based on the gas production amount command. An electrolytic device that updates the current-voltage characteristics stored in the memory unit at predetermined intervals based on the difference between the voltage detected by the voltage sensor and an estimated value of the voltage of the electrolytic cell corresponding to the amount of current distribution, calculated from the current-voltage characteristics read from the memory unit.

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